The acid–base behaviour of hexamine and its N-acetyl derivatives

Abstract

The protonation equilibria and decomposition reactions in aqueous hydrochloric acid of hexamine and its acylated derivatives (2), (3), and (4) have been examined by u.v. and ¹H n.m.r. spectroscopy. pK_a Values at 25 °C are: hexamine 4.89, 3,7-diacetyl-1,3,5,7-tetra-azabicyclo[3.3.3.1]nonane (DAPT) 0.7, 1,3,5,7-tetra-acetyl-1,3,5,7-tetra-azacyclo-octane (TAT)-2.5, and 1,3,5-triacelyl-1,3,5-triaza cyclohexane (TRAT)–2.3. Rates of decomposition of the protonated substrates decrease in the order DAPT > TAT > hexamine.

Reaction of hexamine with picryl acetate may involve nucleophilic catalysis via the N-acetylhexaminium cation (6).